This relates generally to graphics processing and, particularly, to rasterization.
Power and efficiency for graphics processors is important. Substantial efforts have gone into assuring that unnecessary graphics processing operations are avoided. Depth culling is an example of a process for avoiding processing certain parts of a depiction when those parts would be occluded by other parts of the depiction. This saves power and energy and improves the performance of the system.
Commonly, each frame of a plurality of frames making up a video depiction may be rendered one after another. Typically, the entire frame is rendered, even though it is known that, in some cases, portions of the frame do not change from one frame to the other. However, manually keeping track of which regions need updating and rendering only those regions that need updating involves significant bookkeeping and software complexity. In addition, since the programmable stages transform and shade the primitives, identifying regions that need updating often involves a significant amount of work.